Submission #830157

#	Time	Username	Problem	Language	Result	Execution time	Memory
830157		NK_	Cryptography (NOI20_crypto)	C++17	100 / 100	474 ms	22128 KiB

Crypto

// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>

using namespace std;
 
#define nl '\n'
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define sz(x) int(x.size())
 
template<class T> using V = vector<T>;
using vi = V<int>;
using ll = long long;
using pi = pair<int, int>;
using vpi = V<pi>;
using vl = V<ll>;
using db = long double;

const ll MOD = 1e9 + 7;

#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;

template<class T> using iset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

int main() {
	cin.tie(0)->sync_with_stdio(0);
	

	int N; cin >> N;
	vl fact = {1}; for(int i = 1; i < N; i++) fact.pb((fact.back() * 1LL * i) % MOD);

	vi A(N); for(auto& x : A) cin >> x;

	vi X = A; sort(begin(X), end(X));
	for(auto& x : A) x = lower_bound(begin(X), end(X), x) - begin(X);

	iset<int> have; for(int i = 0; i < N; i++) have.insert(i);

	ll ans = 0;
	for(int i = 0; i < N; i++) {
		ll l = have.order_of_key(A[i]);
		// cout << l << endl;

		ans += (l * 1LL * fact[N - 1 - i]) % MOD;
		ans %= MOD;

		have.erase(A[i]);
	}

	cout << (ans + 1) % MOD << nl;

    return 0;
}

• Subtask 1: 5 / 5
• Subtask 2: 9 / 9
• Subtask 3: 10 / 10
• Subtask 4: 11 / 11
• Subtask 5: 21 / 21
• Subtask 6: 13 / 13
• Subtask 7: 19 / 19
• Subtask 8: 12 / 12